I don't believe there is "free" hardware. However there is open source hardware such as Arduino but it does not suit for industrial automation applications.

Automation is a very large domain, so I will only give something that just came to mind: Citect Scada is a free SCADA development software(with some small limitations for the free version); (it is used in industry). Indeed, as said in previous responses, cheaper hardware solutions are microcontrollers(easier with Ardruino) as well as FPGA generally for signal analysis. For more answers please provide more details.

ok, thank you for all us. I will review the proposed topics and then I imagine new questions emerge.